The present invention relates generally to the field of filters and, in particular, to a dual-mode resonator for use in, for example, a cavity filter.
Wireless telecommunications systems transmit signals to and from wireless terminals using radio frequency (RF) signals. A typical wireless system includes a plurality of base stations that are connected to the public switched telephone network (PSTN) via a mobile switching center (MSC). Each base station includes a number of radio transceivers that are typically associated with a transmission tower. Each base station is located so as to cover a geographic region known colloquially as a xe2x80x9ccell.xe2x80x9dEach base station communicates with wireless terminals, e.g. cellular telephones, pagers, and other wireless units, located in its geographic region or cell.
A wireless base station includes a number of modules that work together to process RF signals. These modules typically include, by way of example, mixers, amplifiers, filters, transmission lines, antennas and other appropriate circuits. One type of filter that finds increased use in wireless base stations is known as a microwave cavity filter. These cavity filters include a number of resonators formed in a plurality of cavities so as to provide a selected frequency response when signals are applied to an input of the filter.
One type of resonator structure used in these cavity filters is the dual-mode resonator. The use of dual-mode resonators allows a given filter function to be realized with a smaller size than conventional single mode resonators. Unfortunately, current dual-mode resonators suffer from one or more of various problems. First, many dual-mode resonators are difficult to manufacture due to the shape of the resonator structure, e.g., spherical structures. Further, other dual-mode resonators are too bulky for specific applications. Other problems with existing structures relate to poor heat transfer, limited bandwidth, and difficulties in placing tuning members on the structure.
For the reasons stated above, and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for an improved dual-mode resonator.
The above mentioned problems with dual-mode resonators and other problems are addressed by embodiments of the present invention and will be understood by reading and studying the following specification. Embodiments of the present invention provide a dual-mode resonator that has a cross-like shape and is fixable directly to a surface of an enclosure. In some embodiments, all tuning elements of the dual-mode resonator are provided in the same surface of the enclosure. In some embodiments the shape of the dielectric body is a cross and in other embodiments, the shape is an xe2x80x9cXxe2x80x9d shape. Further, in some embodiments, tuning grooves and tuning elements are positioned proximate the dielectric body to provide coupling between the modes. In some embodiments, a recess is provided in the bottom of the resonator to improve spurious properties.
More particularly, in one embodiment a TE dual-mode resonator is provided. The TE dual-mode resonator has first and second modes. The resonator includes an enclosure having a cavity with an interior surface. The resonator further includes a dielectric resonator body, having a central portion with a plurality of members extending outwardly from the central portion. The dielectric resonator body is coupled directly to the interior surface.